The present invention relates to a DC motor driving apparatus to drive a DC motor.
A DC motor driving apparatus to drive the DC motor is used in a toy car such as an electric radio control car. FIG. 33 is a circuit diagram showing an example of the conventional DC motor driving apparatus used in the electric radio control car.
The DC motor driving apparatus in FIG. 33 is structured by MOS type field effect transistors (hereinafter, called FET) 1 and 2. The FET 1 is used for the speed control of a DC motor 3, and the FET 2 is used for the braking of the DC motor 3. Body diodes 4 and 5 respectively exist inside the FETs 1 and 2. Incidentally, the user connects a Schottky diode 9 to a DC motor 30, or assembles it in the DC motor driving apparatus.
A power supply terminal 301 is connected to a positive electrode of the DC power supply (not shown), and a ground terminal 302 is connected to a negative electrode of the DC power supply. As the DC power supply, for example, a nickel-cadmium cell is used. One terminal 3a of the DC motor 3 is connected to the power supply terminal 301, and the other terminal 3b of the DC motor 3 is connected to the ground terminal 302 through the FET 1. The FET 2 is connected between the one terminal 3a and the other terminal 3b of the DC motor. A control signal SWA is applied on a gate of the FET 1, and a control signal SWB is applied on a gate of FET 2.
The control signal SWA varies between the high level and the low level at the time of advance of the electric radio control car. Thereby, the FET 1 repeats turning ON and OFF. At this time, the control signal SWB is fixed on the low level. Thereby, the FET 2 is turned OFF. As the result, the current flows from the power supply terminal 301 to the ground terminal 302 through the terminal 3a, DC motor 3, terminal 3b, and FET 1, and the DC motor 3 is positively rotated. When the duty ratio of the control signal SWA applied on the gate of the FET 1 is changed, the speed control of the DC motor 3 is conducted.
At the time of braking of the electric radio control car, the control signal SWA is the low level, and the control signal SWB is the high level. Thereby, the FET 1 is turned OFF, and the FET 2 is turned ON, and terminals 3a and 3b are short circuited through the FET 2. As the result, the DC motor 3 is braked.
FIG. 34 and FIG. 35 are circuit diagrams showing the other example of the conventional DC motor driving apparatus used for the electric radio control car. The DC motor driving apparatus shown in FIG. 34 and FIG. 35 is used for positively rotating and reversely rotating the DC motor, and FIG. 34 shows the operation at the time of positive rotation of the DC motor, and FIG. 35 shows the operation at the time of reversal rotation of the DC motor.
In FIG. 34 and FIG. 35, one terminal 31 of the DC motor 30 is connected to the power supply terminal 301 through FET 11, and connected to the ground terminal 302 through the FET 13. The other terminal 32 of the DC motor 30 is connected to the power supply terminal 301 through FET 12, and connected to the ground terminal 302 through the FET 14. Body diodes 21, 22, 23, and 24 respectively exist inside the FETs 11, 12, 13 and 14. The control signals SW1, SW2, Sw3 and SW4 are respectively applied on the gates of the FETs 11, 12, 13, and 14.
The control signal SW1 becomes the high level at the time of positive rotation in FIG. 34, the control signal SW2 becomes the low level, the control signal SW3 becomes the low level, and the control signal SW4 repeatedly changes between the high level and the low level. According to that, the FET 11 is turned ON, FETs 12 and 13 are turned OFF, and FET 14 repeats turned ON and OFF. As the result, as shown by an arrow, the current flows from the power supply terminal 301 to the ground terminal 302 through the FET 11, terminal 31, DC motor 30, terminal 32, and FET 14, and the DC motor 30 is positively rotated. Thereby, the electric radio control car is moved forward.
The control signal SW1 becomes the low level at the time of reversal rotation in FIG. 35, and the control signal SW2 becomes the high level, the control signal SW3 repeatedly changes between the high level and the low level, and the control signal SW4 becomes the low level. According to that, the FET 11 is turned OFF, FET 12 is turned ON, FET 13 repeats turned ON and OFF, and FET 14 are turned OFF. As the result, as shown by an arrow, the current flows from the power supply terminal 301 to the ground terminal 302 through the FET 12, terminal 32, DC motor 30, terminal 31, and FET 13, and the DC motor 30 is reversely rotated. Thereby, the electric radio control car is moved backward.
In the DC motor driving apparatus in FIG. 33, as described above, the FET 1 repeats turned ON and OFF at the time of the speed control. In this case, in the period in which the FET 1 is turned OFF, the counter electromotive force is generated in the DC motor 3. When the counter electromotive force is generated in the DC motor 3, because the drive efficiency of the DC motor 3 by the DC power supply is decreased, the regenerative current by the counter electromotive force is made to flow from the terminal 3b to the terminal 3a through the body diode 5 inside the FET 2, thereby, the counter electromotive force is eliminated.
However, because the for ward voltage of the body diode 5 is comparatively high and about 0.6 V, the heat generation occurs due to the voltage drop, and the heat loss is generated. According to this, the drive efficiency is decreased, and the nickel-cadmium cell which is the DC power supply, is consumed uselessly. As the result, the running time period of the electric radio control car is reduced.
Accordingly, in order to increase the drive efficiency, a Schottky diode 9 is connected to the DC motor 3, and the regenerative current due to counter electromotive force is made to flow from the terminal 3b to the terminal 3a through the Schottky diode 9. The forward voltage of the Schottky diode 9 is about 0.4 V, and because it is not larger than the forward voltage of the body diode 5 inside the FET 2, the regenerative current due to counter electromotive force of the DC motor 3 can be effectively made to flow.
However, a trouble for the user to connect the Schottky diode 9 to the DC motor 3 is generated. Alternatively, when the Schottky diode 9 is previously assembled in the DC motor driving apparatus, the size reduction of the DC motor driving apparatus can not be attained. It is desired that the DC motor driving apparatus is as small as possible so that the user can attach the DC motor driving apparatus to an arbitrary position of the electric radio control car.
Further, although the efficiency when the regenerative current flows to the Schottky diode 9, is improved as compared to the case where the regenerative current flows to the body diode 5 inside the FET 2, it is desired that the drive efficiency is further increased, and the heat generation amount is further decreased.
On the one hand, in the DC motor driving apparatus in FIG. 34 and FIG. 35, because 4 FETs 11 to 14 to drive the DC motor 30 positively and reversely, are used, it is difficult to decrease the size as compared to the DC motor driving apparatus in FIG. 33. Accordingly, generally, when this DC motor driving apparatus is used, the Schottky diode is not connected. Accordingly, the regenerative current due to the counter electromotive force of the DC motor 30 flows to the body diodes 21 and 22 inside the FETs 11 and 12.
In this case, because the heat generation amount due to the voltage drop is large, the drive efficiency is lowered, and nickel-cadmium cell which is the DC power supply, is consumed uselessly. As the result, the running time period of the electric radio control car is reduced.
Accordingly, in also the DC motor driving apparatus which can rotate positively and reversely, it is desired to decrease the heat generation amount and increase the drive efficiency without hindering the size reduction.
The object of the present invention is to provide a DC motor driving apparatus in which the size can be reduced and the drive efficiency is high.
(1) The First Invention
A DC motor driving apparatus according to the first invention is the DC motor driving apparatus to drive a DC motor, which comprising: a first transistor which is inserted into a current path to supply the current from a DC power supply to the DC motor, and is ON/OFF controlled; a second transistor connected between a pair of terminals of the DC motor; and a control circuit for comparing the potential of both terminals of the second transistor, and for turning ON the second transistor when the counter electromotive force is generated in the DC motor.
In the DC motor driving apparatus according to the present invention, when the first transistor is controlled to be turned ON/OFF, the current is supplied from the DC power supply to the DC motor. By controlling the ON time of the first transistor in a predetermined period, the current supplied to the DC motor can be controlled, and the rotation speed of the DC motor can be controlled.
In the OFF time of the first transistor, the counter electromotive force is generated in the DC motor. In this case, the potential of both ends of the second transistor are compared by the control means, and it is detected whether the counter electromotive force is generated in the DC motor, and when the counter electromotive force is generated in the DC motor, the second transistor can be turned ON. When the second transistor is turned ON, the regenerative current flows to the second transistor due to the counter electromotive force generated in the DC motor, and the counter electromotive force is eliminated. Because the drop voltage at the ON time of the second transistor is lower than the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, the ON time of the second transistor is controlled at the real time so that the second transistor is turned ON, only when the counter electromotive force is generated in the DC motor, corresponding to the ON time of the first transistor. Accordingly, under the condition that the regenerative current does not flow, it is prevented that the short circuit is caused between terminals of the DC motor, and the DC motor is braked.
Accordingly, the drive efficiency can be increased while the size reduction of the DC motor driving apparatus is being intended.
(2) The Second Invention
A DC motor driving apparatus according to the second invention is the DC motor driving apparatus to drive the DC motor according to the first invention, wherein
the control circuit includes: a comparator by which the potential of both ends of the second transistor are compared, and which detects that the counter electromotive force is generated in said DC motor, and outputs a detection signal; and a control signal generation circuit to generate a control signal to turn ON the second transistor corresponding to the detection signal outputted from the comparator.
In this case, the potential of both ends of the second transistor are compared by the comparator to detect a counter electromotive force generated in the DC motor, and a detect signal is outputted. A control signal for turning ON the second transistor is generated by the controlling signal generating circuit corresponding to the detecting signal.
(3) The Third Invention
A DC motor driving apparatus according to the third invention is the DC motor driving apparatus to drive a DC motor, which comprising: a first transistor which is inserted into a current path to supply the current from a DC power supply to the DC motor, and controlled to be turned ON/OFF; a second transistor connected between a pair of terminals of the DC motor; and a calculation processing unit which is operated according to a program, and turns ON the second transistor for a predetermined period of time while the first transistor is turned OFF.
In the DC motor driving apparatus according to the present invention, when the first transistor is ON/OFF controlled, the current is supplied from the DC power supply to the DC motor. When the ON time of the first transistor is controlled in a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled.
In the OFF period of the first transistor, the counter electromotive force is generated in the DC motor. In this case, because the calculation processing unit is operated according to the program so that, within the OFF period of the first transistor, the second transistor is turned ON for a predetermined time period, when the counter electromotive force is generated in the DC motor, the second transistor can be turned ON. When the second transistor is turned ON, due to the counter electromotive force generated in the DC motor, the regenerative current flows to the second transistor, thereby, the counter electromotive force is eliminated. Because the drop voltage at the time when the second transistor is ON, is lower as compared to the forward voltage of the Schottky diode, the heat generation amount is smaller, and the heat loss is smaller.
In this case, by making the program so that the ON time of the second transistor is set corresponding to the ON time of the first transistor, the second transistor can be turned ON when the counter electromotive force is generated in the DC motor. Accordingly, it is prevented that, under the condition that the regenerative current does not flow, the short circuit is caused between terminals of the DC motor and the DC motor is braked.
Accordingly, the drive efficiency can be increased while size reduction of the DC motor driving apparatus is being intended.
(4) The Fourth Invention
A DC motor driving apparatus according to the fourth invention is the DC motor driving apparatus to positively rotate and reversely rotate the DC motor, which comprising: a first transistor which is connected between one potential side of the DC power supply and one terminal of the DC motor, and is turned ON at the time of a positive rotation; a second transistor which is connected between the one potential side of the DC power supply and the other terminal of the DC motor, and is turned ON at the time of a reversal rotation; a third transistor which is connected between the other potential side of the DC power supply and the one terminal of the DC motor, and is turned OFF at the time of the positive rotation, and ON/OFF controlled at the time of the reversal rotation; a fourth transistor which is connected between the other potential side of the DC power supply and the other terminal of the DC motor, and ON/OFF controlled at the time of the positive rotation, and turned OFF at the time of the reversal rotation; a first control circuit for comparing the potential of both terminals of the first transistor, and for turning ON the first transistor when the counter electromotive force is generated in the DC motor at the time of. the reversal rotation; and a second control circuit for comparing the potential of both terminals of the second transistor, and for turning ON the second transistor when the counter electromotive force is generated in the DC motor at the time of the positive rotation.
In the DC motor driving apparatus according to the present invention, when the DC motor is positively rotated, the first transistor is turned ON, the third transistor is turned OFF, and the fourth transistor is ON/OFF controlled. Thereby, the current flows from one potential side of the DC power supply to the other potential side of the DC power supply through the first transistor, one terminal, DC motor, the other terminal, and the fourth transistor, and the DC motor is positively rotated. By controlling the ON time of the fourth transistor in a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled.
In the OFF period of the fourth transistor, the counter electromotive force is generated in the DC motor. By the second control means, the potential of both ends of the second transistor is compared, and it is detected whether the counter electromotive force is generated in the DC motor, or not, and when the counter electromotive force is generated in the DC motor, the second transistor can be turned ON. When the second transistor is turned ON, the both terminals of the DC motor is short circuited through the first transistor and the second transistor, and due to the counter electromotive force generated in the DC motor, the regenerative current flows from the other terminal of the DC motor to the one terminal through the second transistor and the first transistor, and the counter electromotive force is eliminated. Because the drop voltage when the first and the second transistors are turned ON, is very low as compared to the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, the ON time of the second transistor is controlled at real time so that the second transistor is turned ON only when the counter electromotive force is generated in the DC motor, corresponding to the ON time of the fourth transistor. Accordingly, it is prevented that the short circuit is caused between terminals of the DC motor, and the DC motor is braked, under the condition that the regenerative current does not flow.
When the DC motor is reversely rotated, the second transistor is turned ON, the third transistor is ON/OFF controlled, and the fourth transistor is turned OFF. Thereby, the current flows from one potential side of the DC power supply through the second transistor, the other terminal, DC motor, one terminal and the third transistor, and the DC motor is reversely rotated. By controlling the ON time of the third transistor in a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled.
In the OFF period of the third transistor, the counter electromotive force is generated in the DC motor. By the first control means, the potential of both ends of the first transistor is compared, and it is detected whether the counter electromotive force is generated in the DC motor, or not, and when the counter electromotive force is generated in the DC motor, the first transistor can be turned ON. When the first transistor is turned ON, the both terminals of the DC motor is short circuited through the first transistor and the second transistor, and due to the counter electromotive force generated in the DC motor, the regenerative current flows from the other terminal of the DC motor to the one terminal through the first transistor and the second transistor, and the counter electromotive force is eliminated. Because the drop voltage when the first and the second transistors are turned ON, is low as compared to the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, the ON time of the first transistor is controlled at real time so that the first transistor is turned ON only when the counter electromotive force is generated in the DC motor, corresponding to the ON time of the third transistor. Accordingly, it is prevented that the short circuit is caused between terminals of the DC motor, and the DC motor is braked, under the condition that the regenerative current does not flow.
Accordingly, the drive efficiency can be increased while size reduction of the DC motor driving apparatus is being intended.
(5) The Fifth Invention
A DC motor driving apparatus according to the fifth invention is the DC motor driving apparatus according to the fourth invention, wherein
a first control circuit includes: a first comparator which compares the potential of both ends of the first transistor, and at the time of reversal rotation, detects that the counter electromotive force is generated in the DC motor, and outputs the first detection signal; and a first control signal generation circuit to generate the first control signal to turn ON the first transistor corresponding to the first detection signal outputted from the first comparator, and a second control circuit includes: a second comparator which compares the potential of both ends of the second transistor, and at the time of positive rotation, detects that the counter electromotive force is generated in the DC motor, and outputs the second detection signal; and a second control signal generation circuit to generate the second control signal to turn ON the second transistor corresponding to the second detection signal outputted from the second comparator.
In this case, the potential of both ends of the first transistor are compared by the first comparator, and it is detected that the counter electromotive force is generated in the DC motor at the time of the reversal rotation, and the first detection signal is outputted. The first control signal to turn ON the first transistor is generated by the first control signal generating circuit corresponding to the first detection signal. Further, the potential of both ends of the second transistor are compared by the second comparator, and it is detected that the counter electromotive force is generated in the DC motor at the time of the positive rotation, and the second detection signal is outputted. The second control signal to turn ON the second transistor is generated by the second control signal generating circuit corresponding to the second detection signal.
(6) The Sixth Invention
A DC motor driving apparatus according to the sixth invention is the DC motor driving apparatus to positively rotate and reversely rotate a DC motor, which comprising: a first transistor which is connected between one potential side of the DC power supply and one terminal of the DC motor, and is turned ON at the time of a positive rotation; a second transistor which is connected between the one potential side of the DC power supply and the other terminal of the DC motor, and is turned ON at the time of a reversal rotation; a third transistor which is connected between the other potential side of the DC power supply and the one terminal of the DC motor, and is turned OFF at the time of the positive rotation, and ON/OFF controlled at the time of the reversal rotation; a fourth transistor which is connected between the other potential side of the DC power supply and the other terminal of the DC motor, and ON/OFF controlled at the time of the positive rotation, and turned OFF at the time of the reversal rotation; and a calculation processing unit which is operated according to a program, and turns ON the first transistor for a predetermined period of time in a period in which the third transistor is turned OFF at the time of the reversal rotation, and turns ON the second transistor for a predetermined period of time in a period in which the fourth transistor is turned OFF at the time of the positive rotation.
In the DC motor driving apparatus according to the present invention, when the DC motor is positively rotated, the first transistor is turned ON, the third transistor is turned OFF, and the fourth transistor is ON/OFF controlled. Thereby, the current flows from one potential side of the DC power supply to the other potential side of the DC power supply through the first transistor, one terminal, DC motor, the other terminal, and the fourth transistor, and the DC motor is positively rotated. By controlling the ON time of the fourth transistor in a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled.
In the OFF period of the fourth transistor, the counter electromotive force is generated in the DC motor. In this case, because the calculation processing unit is operated according to the program so that the second transistor is turned ON for a predetermined time period in the period in which the fourth transistor is turned OFF, when the counter electromotive force is generated in the DC motor, the second transistor can be turned ON. When the second transistor is turned ON, the both terminals of the DC motor is short circuited through the first transistor and the second transistor, and due to the counter electromotive force generated in the DC motor, the regenerative current flows from the other terminal of the DC motor to the one terminal through the second transistor and the first transistor, and the counter electromotive force is eliminated. Because the drop voltage when the first and the second transistors are turned ON, is low as compared to the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, by making the program so that the ON time of the second transistor is set corresponding to the ON time of the fourth transistor, the second transistor can be turned ON only when the counter electromotive force is generated in the DC motor. Accordingly, it is prevented that the short circuit is caused between terminals of the DC motor and the DC motor is braked, under the condition that the regenerative current does not flow.
When the DC motor is reversely rotated, the second transistor is turned ON, the third transistor is ON/OFF controlled, and the fourth transistor is turned OFF. Thereby, the current flows from one potential side of the DC power supply through the second transistor, the other terminal, DC motor, one terminal and the third transistor, and the DC motor is reversely rotated. By controlling the ON time of the third transistor in a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled.
In the OFF period of the third transistor, the counter electromotive force is generated in the DC motor. In this case, because the calculation processing unit is operated according to the program so that the first transistor is turned ON for a predetermined time period in the period in which the third transistor is turned OFF, when the counter electromotive force is generated in the DC motor, the first transistor can be turned ON. When the first transistor is turned ON, the both terminals of the DC motor is short circuited through the first transistor and the second transistor, and due to the counter electromotive force generated in the DC motor, the regenerative current flows from the one terminal of the DC motor to the other terminal through the first transistor and the second transistor, and the counter electromotive force is eliminated. Because the drop voltage when the first and the second transistors are turned ON, is low as compared to the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, by making the program so that the ON time of the first transistor is set corresponding to the ON time of the third transistor, the first transistor can be turned ON when the counter electromotive force is generated in the DC motor. Accordingly, it is prevented that the short circuit is caused between terminals of the DC motor, and the DC motor is braked, under the condition that the regenerative current does not flow.
Accordingly, the drive efficiency can be increased while size reduction of the DC motor driving apparatus is being intended.
(7) The Seventh Invention
A DC motor driving apparatus according to the seventh invention is the DC motor driving apparatus to drive a DC motor, which comprising: a first switching means which is inserted into a current path to supply the current from a DC power supply to the DC motor, and ON/OFF controlled; a second switching means which is connected between a pair of terminals of the DC motor; and a control means for comparing the potential of both ends of the second switching means, and for turning ON the second switching means when the counter electromotive force is generated in the DC motor.
In the DC motor driving apparatus according to the present invention, when the first switching means is ON/OFF controlled, the current is supplied from the DC power supply to the DC motor. When the ON time of the first switching means is controlled within a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled.
During the OFF period of the first switching means, the counter electromotive force is generated in the DC motor. In this case, by comparing the potential of both ends of the second switching means by the control means, it is detected whether the counter electromotive force is generated in the DC motor, and when the counter electromotive force is generated in the DC motor, the second switching means can be turned ON. When the second switching means is turned ON, the regenerative current flows to the second switching means by the counter electromotive force generated in the DC motor, and the counter electromotive force is deleted. Because the drop voltage in the ON time of the second switching means is not higher than the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, the ON time of the second switching means is controlled at. real time so that the second switching means is turned ON only when the counter electromotive force is generated in the DC motor. Accordingly, it is prevented that both terminals of the DC motor are short circuited and the DC motor is braked, under the condition that regenerative current does not flow.
Accordingly, the drive efficiency can be increased while the size reduction of the DC motor driving apparatus is being intended.
(8) The eighth invention
A DC motor driving apparatus according to the eighth invention is the DC motor driving apparatus according to the seventh invention, wherein
the control means includes: a counter electromotive force detection means for comparing the potential of both ends of the second switching means, and detecting that the counter electromotive force is generated in the DC motor; and a switching control means for turning ON the second switching means corresponding to the detection of the counter electromotive force by the counter electromotive force detection means.
In this case, the potential of both ends of the second switching means are compared by the counter electromotive force detection means, and it is detected that the counter electromotive force is generated in the DC motor. The second switching means is turned ON by the switching control means corresponding to the detection of the counter electromotive force by the counter electromotive force detection means.
(9) The Ninth Invention
A DC motor driving apparatus according to the ninth invention is the DC motor driving apparatus to drive a DC motor, which comprising: a first switching means which is inserted into a current path to supply the current from a DC power supply to the DC motor, and ON/OFF controlled; a second switching means which is connected between a pair of terminals of the DC motor; and a calculation processing means for operating according to a program, and for turning ON the second switching means for a predetermined time while the first switching means is turned OFF.
In the DC motor driving apparatus according to the present invention, when the first switching means is ON/OFF controlled, the current is supplied from the DC power supply to the DC motor. By controlling the ON time of the first switching means within a predetermined period, the current supplied to the DC motor can be controlled, and the rotation speed of the DC motor can be controlled.
Within the OFF period of the first switching means, the counter electromotive force is generated in the DC motor. In this case, because the calculation processing means is operated according to the program so that the second switching means is turned ON for a predetermined time within a period in which the first switching means is turned OFF, the second switching means can be turned ON when the counter electromotive force is generated in the DC motor. When the second switching means is turned ON, by the counter electromotive force generated in the DC motor, the regenerative current flows to the second switching means, and the counter electromotive force is deleted. Because the drop voltage in the ON time of the second switching means is not higher than the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, when the program is made so that the ON time of the second switching means is set corresponding to the ON time of the first switching means, the second switching means can be turned ON when the counter electromotive force is generated in the DC motor. Accordingly, it is prevented that both terminals of the DC motor are short circuited and the DC motor is braked, under the condition that the regenerative current does not flow.
Accordingly, the drive efficiency can be increased while the size reduction of the DC motor driving apparatus is being intended.
(10) The Tenth Invention
A DC motor driving apparatus according to the tenth invention is the DC motor driving apparatus to positively rotate and reversely rotate the DC motor, which comprising: the first switching means which is connected between one potential side of the DC power supply and one terminal of the DC motor, and turned ON at the time of the positive rotation; the second switching means which is connected between one potential side of the DC power supply and the other terminal of the DC motor, and turned ON at the time of the reversal rotation; the third switching means which is connected between the other potential side of the DC power supply and one terminal of the DC motor, and turned ON at the time of the positive rotation, and ON/OFF controlled at the time of the reversal rotation; the fourth switching means which is connected between the other potential side of the DC power supply and the other terminal of the DC motor, and turned ON at the time of the positive rotation, and turned OFF at the time of the reversal rotation; the first control means for comparing the potential of both ends of the first switching means, and for turning ON the first switching means when the counter electromotive force is generated in the DC motor, at the time of the reversal rotation; and the second control means for comparing the potential of both ends of the second switching means, and for turning ON the second switching means when the counter electromotive force is generated in the DC motor, at the time of the positive rotation.
In the DC motor driving apparatus according to the present invention, at the positive rotation of the DC motor, the first switching means is turned ON, the third switching means is turned OFF, and the forth switching means is ON/OFF controlled. Thereby, the current flows from the one potential side of the DC power supply to the other potential side of the DC power supply, through the first switching means, one terminal, DC motor, the other terminal and the fourth switching means, and the DC motor is positively rotated. By controlling the ON time of the fourth switching means within a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled.
During the OFF period of the fourth switching means, the counter electromotive force is generated in the DC motor. By comparing the potential of both ends of the second switching means by the second control means, it is detected whether the counter electromotive force is generated in the DC motor, and when the counter electromotive force is generated in the DC motor, the second switching means can be turned ON. When the second switching means is turned ON, both terminals of the DC motor are short circuited through the first switching means and the second switching means, and the regenerative current flows from the other terminal of the DC motor to the one terminal through the second switching means and the first switching means, by the counter electromotive force generated in the DC motor, and the counter electromotive force is deleted. Because the drop voltage in the ON time of the first and second switching means is very lower than the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, the ON time of the second switching means is controlled at real time so that the second switching means is turned ON only when the counter electromotive force is generated in the DC motor, corresponding to ON time of the forth switching means. Accordingly, it is prevented that both terminals of the DC motor are short circuited and the DC motor is braked, under the condition that regenerative current does not flow.
At the time of the reversal rotation of the DC motor, the second switching means is turned ON, the third switching means is ON/OFF controlled, and the fourth switching means is tuned OFF. Thereby, the current flows from the one potential side of the DC power supply through the second switching means, the other terminal, DC motor, one terminal, and the third switching means, and the DC motor is reversely rotated. By controlling the ON time of the third switching means in a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled.
During the OFF period of the third switching means, the counter electromotive force is generated in the DC motor. By comparing the potential of both ends of the first switching means by the first control means, it is detected whether the counter electromotive force is generated in the DC motor, and when the counter electromotive force is generated in the DC motor, the first switching means can be turned ON. When the first switching means is turned ON, both terminals of the DC motor are short circuited through the first switching means and the second switching means, and the regenerative current flows from the one terminal of the DC motor to the other terminal through the first switching means and the second switching means, by the counter electromotive force generated in the DC motor, and the counter electromotive force is deleted. Because the drop voltage in the ON time of the first and second switching means is lower than the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, the ON time of the first switching means is controlled at real time so that the first switching means is turned ON only when the counter electromotive force is generated in the DC motor, corresponding to ON time of the third switching means. Accordingly, it is prevented that both terminals of the DC motor are short circuited and the DC motor is braked, under the condition that regenerative current does not flow.
Accordingly, the drive efficiency can be increased while the size reduction of the DC motor driving apparatus is being intended
(11) The eleventh invention
A DC motor driving apparatus according to the eleventh invention is the DC motor driving apparatus according to the tenth invention, wherein
the first control means includes: the first counter electromotive force detection means for comparing the potential of both ends of the first switching means, and detecting that the counter electromotive force is generated in the DC motor at the time of the reversal rotation; and the first switching control means for turning ON the first switching means corresponding to the detection of the counter electromotive force by the first counter electromotive force detection means, and the second control means includes: the second counter electromotive force detection means for comparing the potential of both ends of the second switching means, and detecting that the counter electromotive force is generated in the DC motor, at the time of the positive rotation; and the second switching control means for turning ON the second switching means corresponding to the detection of the counter electromotive force by the second counter electromotive force detection means.
In the DC motor driving apparatus according to the present invention, the potential of both ends of the first switching means are compared by the first counter electromotive force detection means, and it is detected that the counter electromotive force is generated in the DC motor at the time of the reversal rotation. The first switching means is turned ON by the first switching control means corresponding to the detection of the counter electromotive force by the first counter electromotive force detection means. Further, the potential of both ends of the second switching means are compared by the second counter electromotive force detection means, and it is detected that the counter electromotive force is generated in the DC motor at the time of the positive rotation. The second switching means is turned ON by the second switching control means corresponding to the detection of the counter electromotive force by the second counter electromotive force detection means.
(12) Twelfth Invention
A DC motor driving apparatus according to the twelfth invention is the DC motor driving apparatus to positively rotate and reversely rotate the DC motor, which comprising: the first switching means which is connected between one potential side of the DC power supply and one terminal of the DC motor, and turned ON at the time of the positive rotation; the second switching means which is connected between one potential side of the DC power supply and the other terminal of the DC motor, and turned ON at the time of the reversal rotation; the third switching means which is connected between the other potential side of the DC power supply and one terminal of the DC motor, and turned OFF at the time of the positive rotation, and ON/OFF controlled at the time of the reversal rotation; the fourth switching means which is connected between the other potential side of the DC power supply and the other terminal of the DC motor, and ON/OFF controlled at the time of the positive rotation, and turned OFF at the time of the reversal rotation; and a calculation processing means for operating according to a program, and for turning ON the first switching means for a predetermined time while the third switching means is turned OFF at the time of the reversal rotation, and for turning ON the second switching means for a predetermined time while the fourth switching means is turned OFF at the time of the positive rotation.
In the DC motor driving apparatus according to the present invention, at the time of the positive rotation of the DC motor, the first switching means is turned ON, the third switching means ids turned OFF, and the fourth switching means is ON/OFF controlled. Thereby, the current flows from the one potential side of the DC power supply to the other potential side of the DC power supply through the first switching means, one terminal, DC motor, the other terminal and the fourth switching means, and the DC motor is positively rotated By controlling the ON time of the fourth switching means in a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled
During the OFF period of the fourth switching means, the counter electromotive force is generated in the DC motor. In this case, because the calculation processing means is operated according to the program so that the second switching means is turned ON for a predetermined time during the period in which the fourth switching means is turned OFF, the second switching means can be turned ON when the counter electromotive force is generated in the DC motor. When the second switching means is turned. ON, both terminals of the DC motor are short circuited through the first switching means and the second switching means, and the regenerative current flows from the other terminal to the one terminal through the second switching means and the first switching means by the counter electromotive force generated in the DC motor, and the counter electromotive force is deleted. Because the drop voltage in the ON time of the first and second switching means is lower than the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, when the program is made so that the ON time of the second switching means is set corresponding to the ON time of the fourth switching means, the second switching means can be turned ON only when the counter electromotive force is generated in the DC motor. Accordingly, it is prevented that both terminal of the DC motor are short circuited and the DC motor is braked, under the condition that the regenerative current does not flow.
At the time of the reversal rotation of the DC motor, the second switching means is turned ON, the third switching means is ON/OFF controlled, and the fourth switching means is tuned OFF. Thereby, the current flows from the one potential side of the DC power supply through the second switching means, the other terminal, DC motor, one terminal, and the third switching means, and the DC motor is reversely rotated. By controlling the ON time of the third switching means in a predetermined period, the current supplied to the DC motor is controlled, and the rotation speed of the DC motor can be controlled.
During the OFF period of the third switching means, the counter electromotive force is generated in the DC motor. By comparing the potential of both ends of the first switching means by the first control means, it is detected whether the counter electromotive force is generated in the DC motor, and when the counter electromotive force is generated in the DC motor, the first switching means can be turned ON. When the first switching means is turned ON, both terminals of the DC motor are short circuited through the first switching means and the second switching means, and the regenerative current flows from the one terminal of the DC motor to the other terminal through the first switching means and the second switching means, by the counter electromotive force generated in the DC motor, and the counter electromotive force is deleted. Because the drop voltage in the ON time of the first and second switching means is lower than the forward voltage of the Schottky diode, the heat generation amount is small, and the heat loss is small.
In this case, when the program is made so that the ON time of the first switching means is set corresponding to the ON time of the third switching means, the first switching means can be turned ON when the counter electromotive force is generated in the DC motor. Accordingly, it is prevented that both terminals of the DC motor are short circuited and the DC motor is braked, under the condition that regenerative current does not flow.
Accordingly, the drive efficiency can be increased while the size reduction of the DC motor driving apparatus is being intended.
(13) The Thirteenth Invention
A DC motor driving apparatus according to the thirteenth invention is the DC motor driving apparatus according to the third, the sixth, the ninth, or the twelfth invention, wherein
a predetermined time is the time previously determined to delete the counter electromotive force generated in the DC motor. Thereby, the counter electromotive force generated in the DC motor is completely deleted.